Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 5 2005 10.5194/acpd-5-9291-2005 http://www.atmos-chem-phys-discuss.net/5/9291/2005/ http://www.atmos-chem-phys-discuss.net/5/9291/2005/acpd-5-9291-2005.html http://www.atmos-chem-phys-discuss.net/5/9291/2005/acpd-5-9291-2005.pdf 9291 9324 2005-09-28 A computationally efficient inorganic atmospheric aerosol phase equilibrium model (UHAERO) N. R. Amundson A. Caboussat J. W. He A. V. Martynenko V. B. Savarin J. H. Seinfeld K. Y. Yoo Department of Mathematics, University of Houston, Houston, USA Ecole Nationale Supérieure de Techniques Avancées, Paris, France Departments of Chemical Engineering and Environmental Science and Engineering, California Institute of Technology, Pasadena, USA Department of Chemical Engineering, Seoul National University of Technology, Seoul, Korea A variety of thermodynamic models have been developed to predict inorganic gas-aerosol equilibrium. To achieve computational efficiency a number of the models rely on a priori specification of the phases present in certain relative humidity regimes. Presented here is a new computational model, named UHAERO, that is both efficient and rigorously computes phase behavior without any a priori specification. The computational implementation is based on minimization of the Gibbs free energy using a primal-dual method, coupled to a Newton iteration. The mathematical details of the solution are given elsewhere. The model also computes deliquescence and crystallization behavior without any a priori specification of the relative humidities of deliquescence or crystallization. Detailed phase diagrams of the sulfate/nitrate/ammonium/water system are presented as a function of relative humidity at 298.15 K over the complete space of composition.